1. Field of the Invention
The present invention relates to an antenna apparatus, particularly to a small size flat type antenna apparatus used for the Global Positioning System (GPS) antenna or the like.
2. Description of Related Art
With the recent development of small size communication devices (for example, the GPS type car navigation apparatus, the portable navigation apparatus, the satellite wave receiving device and the like) such as mobile communication devices, downsizing and technological advances regarding the antenna apparatus which are used in such devices are desired. In this regard, a flat type antenna apparatus (for example, the circular polarized patch antenna or the like) among antenna apparatuses is structurally thin and small, and has an advantage that the integration with the semiconductor circuit is relatively easy. Therefore, it is broadly applied as an antenna for small size communication devices.
For example, there is known an antenna apparatus which comprises a substrate formed with a high dielectric material such as ceramic, a radiating element provided on the surface of the substrate and a circuit substrate as a flat type antenna apparatus (for example, see JP2001-339232A, JP2001-339233A and JP2001-339234A). In the antenna apparatus which has the above described structure, the capacitance of the antenna can be assured by the high dielectric material. Therefore, the resonance frequency becomes low, and the radiation conductive plate can be downsized.
However, ceramic is heavy and expensive. A thin film of silver is generally used for the radiating element provided on the surface thereof, and the thin film of silver is also expensive. Further, equipments such as the calcinating equipment for ceramic, the printing equipment for the thin film of silver and the like are needed. Therefore, resultingly, there is a problem that the manufacture cost of the antenna apparatus becomes expensive when ceramic is mounted and when the thin film of silver is formed in the small size flat type antenna apparatus as described in JP2001-339232A.
Further, ceramic contributes to the downsizing of the antenna apparatus because ceramic has very high dielectric constant. However, the circumference of the pattern needs to be adjusted by cutting a slit in the pattern of the patch for each apparatus because the dielectric constant and the capacitance vary. There is also a problem that the manufacture cost of the antenna apparatus increases as a result because the variation control of the dielectric constant and the capacitance is not necessarily easy, and the extraction rate is low.